"Nothing's going to happen for eight to ten hours, at least," Cardenas said briskly. "So let's all get a decent sleep."

Greg agreed. I'll get the people on duty to call if there's any change in his condition."

Joanna said, "I can sleep here, on the chair."

"No," Greg said firmly, taking her by the arm. "You sleep in your quarters, on a bunk. Doctor's orders."

Reluctantly, Joanna allowed her elder son to lead her out of the observation room and toward the suite that Anson had vacated for her. She almost felt grateful to Greg for his forceful tenderness.

Small as viruses, millions upon millions of nanomachines flowed through Doug's blood stream like an army of repair personnel eager to get to work. Blind, deaf, without the intelligence of an amoeba, they were tuned to the chemical signatures that cells emit In their world of the ultrasmall, where a bacterium is as gigantic and complex as a shopping mall, they were guided by the shapes of the molecules swarming around them.

Built to seek out specific types of molecules, they quickly spread through the enormous labyrinthine ways of Doug's failing body. With receptors barely a thousand atoms long they touched and tested every molecule they came in contact with. Hardly any of them were of interest to the nanomachines; they merely touched, found that the molecule did not fit precisely into their receptor jaws, and left the molecule behind. Like a lock seeking its proper key, each nanomachine blindly searched the teeming liquid world within Doug's wasting body.

When they did find a molecule that nested properly in their receptors, they clamped onto it and tore it apart into its individual atoms: carbon, hydrogen, nitrogen, oxygen and the rarer metals and minerals. Then other nanomachines seized the freed atoms and combined them into new molecules, new nutrients for the cells that were damaged and dying.

Deep into the cells they penetrated, into the nucleus where the huge double spiral DNA molecules worked as templates for building vital proteins. Here was where the most crucial damage had been done. The links between the two intertwining spirals, the base pairs that were the genes themselves, had been heavily damaged by the ionizing radiation. Where the nanomachines saw a break in this vital linkage, where base pairs had been broken or mismatched, the nanomachines rebuilt the bases and linked them correctly. Like vastly complex three-dimensional jigsaw puzzles, the DNA molecules were put together properly by the busily hurrying nanomachines, much as Doug's own natural enzymes were valiantly trying to do. Together, the polymerases and the nanomachines worked frantically to repair the massive DNA molecules.

They worked with blinding speed, although time meant nothing to them. In this nanometer universe a thousandth of a second stretched like years and decades. In microseconds they repaired damaged cells and then flowed onward, seeking, testing, destroying damaged areas, rebuilding molecules for the growth of healthy new cells. DNA repair was more intricate, more demanding. It took whole tenths of seconds to repair a damaged DNA molecule. Millions of cells and DNA molecules were repaired each minute. But there were so many billions more to reach.

Killifer was not accustomed to being a hero. He was surprised to see that Jinny Anson and more than a dozen others were waiting for him at The Pit when he led his weary team out of their Jobbers. Anson pounded him on the back and insisted on taking him to The Cave for a drink. She even provided the booze.

"You did damned fine out there," Anson said, leaning back in her chair, grinning across the table at Killifer.

Unshaven, grimy, Killifer relished the glow of the rocket juice that laced his coffee. And the glow of her approval.

"Yep," Anson said, "now I can turn over the job to Greg Masterson and leave on schedule and get myself married."

Shocked, Killifer blurted, "Married?"

"The Dragon Lady wanted me to stay on until the expedition got back. So now you're back and I can head for San Antone with a clear conscience."

I'll be damned," Killifer said.

Anson's expression sobered. "Shame about Brennart, though."

"Yeah."

"What went wrong with his hopper, do you think? Why'd it die out there?"

Shifting nervously in his chair, Killifer said, "Radiation must've knocked out the electrical system. Something like ithat."

"Somebody'll have to check it out when you go back there," said Anson.

"Yeah. Right"

"But we've got the polar region, that's what's really important."

"How's the Stavenger kid?"

She shrugged. "They're working on him."

"Is he gonna pull through?"

With a shake of her head, Anson replied, "Damned if I know. They've dragooned some high-priced talent here to try nanotherapy on him, but nobody knows if it'll work."

Killifer was silent for a moment 'And, uh, the astronomer...' Don't look too anxious, he warned himself. "What's her name?"

"The Korean? Rhee. Bianca Rhee."

"Yeah. How's she doing?"

"Okay, I guess, Why're you so interested in her?"

I'm not," he said quickly. "Just-she flew out with Stavenger, I wanted to make sure she's okay."

"She's probably on duty right now. Check the astronomy dome if you want to see her."

"Yeah," Killifer said. "Maybe I will. After I clean up some."

Anson grinned lopsidedly. "Do I detect a romance?"

"Naw," Killifer said. Then wished he hadn't.

It made no difference. Anson, her mind turning toward her own marriage, said, "Don't be coy, Jack. You're a hero now. You can have your pick of the love-starved women of Moonbase, I betcha."

Killifer grinned at the idea. Yeah, he told himself. I'm a big friggin' hero. As long as nobody finds out what I did to Brennart and Doug Stavenger.

She wasn't at the astronomy dome. The place was empty. Nothing there except a half dozen display screens and a computer humming to itself.

Killifer slipped into the empty chair and used the computer to find where Rhee's quarters were. He phoned; no answer.

Maybe I can duck in there, he thought, and find the cement cover. Then when we go back to Mt. Wasser I can stick it back onto the hopper and nobody'll ever know what happened.

He headed for Rhee's quarters.

Bianca Rhee was at the infirmary, staring through the observation room's window at Doug's inert form, still swathed in the light blue cooling blankets. The medic on duty told her that Doug wasn't expected to come out of his hypothermic coma for days. But with oriental patience, Rhee sat as immobile as he was and watched over him.

The accordion-fold door was locked but Killifer got past it easily enough, using his plastic ID card to spring the bolt. Rhee's one room looked as neat as a real-estate model. Everything in place. Bed, desk, bureau: standard issue, same as every other apartment in Moonbase. The only signs of individuality were a set of framed photographs on the bureau, family from the looks of mem, and a delicate small lacquered vase with an imitation flower in it Killifer went swiftly through the desk drawers. It wasn't there. Then the bureau. Nothing but clothes. And a pair of toe shoes, for god's sake, beat up as hell and just as smelly. The closet Not there either.

He stood for an agonized moment in the middle of the room, so small that he could almost touch its opposing walls by stretching out his arms. It's got to be in here someplace, he told himself. Where? He checked under her sink. Nothing.

Where the hell is it? She can't be carrying it around with her. Can she?

Then he saw it. So obvious that he knew she wasn't trying to hide it. She was using it as a base, beneath the flower vase. Its gold plating complimented the deep burgundy of the vase nicely. Killifer felt his pent-up breath ease out of him. Feeling enormously relieved, he slipped the cover out from under the vase and tucked it into the back pocket of his coveralls. : Cautiously, he cracked the apartment door open. Two people were coming down the tunnel, talking earnestly. Killifer let them pass, then eased himself out behind them, closed the door and heard its lock click, then walked swiftly in the other direction.

With the cermet cover in his pocket "It's been almost twelve hours," Joanna said to Zimmerman. "Shouldn't we see some change? Some improvement?"

She and Greg, the Swiss scientist and Cardenas were in the infirmary's observation room again. A young oriental woman had been sitting there when Joanna entered, but she got up and left so swiftly that Joanna didn't even get the chance to ask her who she was. She was wearing the pumpkin orange coveralls of the scientific staff; maybe she was working for Zimmerman, Joanna thought "There is improvement' Zimmerman said, pointing a stubby finger at the monitors above Doug's bed. "Look at his vital signs. Heartbeat is stronger. Blood pressure is almost normal. Kidney function is returning.

"But he hasn't moved," Greg said, peering through the window.

"That's to be expected," Cardenas said softly. "He's using all his energy internally."

"I believe," Zimmerman said, pulling out another long black cigar, "that it will be possible to remove the hypothermic blankets in another two hours." He chomped on the cigar with relish. "Three, at most."

"And then?" Joanna asked.

With a sloppy shrug, Zimmerman said, "And then, sooner or later he will wake up and ask for food. He will be very hungry. Very!"

"He'll be cured?"

"If that's the word you want to use, yes. He will begin to function normally again." Zimmerman grinned around his cigar.

Joanna looked from his florid, fleshy face through the window at her son. Doug will be cured! This nightmare will be over. Even Greg looked pleased, she thought.

"He'll be all right," Cardenas said to her. "The nanomachines are working inside him."

For an instant Joanna wanted to throw her arms around Zimmerman and kiss him. But she controlled herself and the moment passed. As calmly as she could, she said to him, "Dr. Zimmerman, I want to find some way to repay you. What can I do?"

"Let me go home," he snapped.

Laughing, Joanna said, "Of course. Of course. As soon as Doug regains consciousness-although I suppose you'll want to see him after he's on his feet again."

"Yes, yes. You have virtual reality equipment here. I can examine him using VR."

"But won't you want to see him in person?" Joanna asked. "In the flesh?"

Zimmerman shook his head violently, making his cheeks waddle. "I am not coming back to this cavern! Never!"

"All right. Doug can see you in Basel, then."

"That will be impossible, I fear."

"Why not?"

"A young man who is carrying millions of self-replicating nanomachines in his body would not be a welcome person on Earth. I doubt that he would be able to get past your own customs and immigration inspectors."

Feeling confused, Joanna sat down on the couch facing the observation window. "I don't understand."

Cardenas sat next to her. Zimmerman remained standing. Greg was staring at him now.

"Your son is carrying nanomachines," Zimmerman said. "He would not be permitted to land on Earth. Every nation has laws against nanomachines in the human body. They are all afraid of nanomonsters."

"But the bugs will flush out of his system once they've finished their work," Joanna said, then added, "Won't they?"

Zimmerman would not meet her eye.

Joanna turned to Cardenas. "What's he talking about?"

With a careful sigh, Cardenas said, "You know about the laws against injecting nanomachines into human patients, don't you?"

"Oh, that stupid stuff."

"It's stupid, all right, but it's still the law. If Doug still has any trace of nanomachines in his system, he'll be stopped by the immigration inspectors at any rocket port on Earth. They're terrified of nanobugs running amok and killing people."

"But-"

"May I point out," Zimmerman interjected, "that perhaps these laws are not so stupid after all. How many military establishments have supported research into nanoweapons? Nanotechnology could make biological warfare look like child's games."

"But there are laws against military applications of nanotechnology," Greg objected. "International treaties."

"Yes, of course. Those are precisely the laws that do not allow nanomachines to be injected into human patients."

"But Doug isn't going to hurt anybody!" Joanna said.

"'Still, he will be carrying these self-replicating nano-machines for as long as he lives."

"What?" Startled, Joanna snapped, "You didn't tell me that-'""

"That," said Zimmerman, bending to put his cigar-clenched face close to hers, "is the payment I extract from you."

"Payment? What are you talking about?"

"Your son is my living laboratory, Madam; my lifetime experiment. He carries self-replicating nanotnachines within his body. Forever."

"What have you done?" Joanna cried.

"I have given your son a great gift, Madam," Zimmerman replied.

Before Joanna could say anything, Cardenas said, "You've enhanced his immune system."

Zimmerman took the soggy cigar from his mouth. "Yah, but there is more to it than that."

"What?" Joanna demanded.

Almost smirking, Zimmerman said, "Frankly, I do not know. No one can know. We have no experience with self-replicating nanomachines in the human body."

"You've turned my son into-"

"An experiment. A living laboratory," Zimmerman said. "A step toward the perfection of nanotherapy."

Before Joanna could reply, Cardenas said, "It's a great gift, really! His immune system is now so enhanced he'll probably never even catch a cold anymore."

Zimmerman nodded. "Perhaps. The machines should be able to adapt to destroy microbes and viruses that invade his body."

"But you don't know for certain what they'll do," Greg said, his voice hollow.

"They should also repair effects of aging and any injuries he might incur," Zimmerman added, still speaking to Joanna. "Your son will most likely live a long, long time, Frau Stavenger."